Conventionally, as an external storage medium of a host device such as a personal digital assistant, a desktop model computer, a notebook model computer, a portable telephone, an audio device or a home electrical appliance, a removable card-like small IC memory device containing a semiconductor memory that can be inserted into/removed from these devices has been used.
The memory device of this type generally contains a non-volatile semiconductor memory (IC memory) such as a flash memory, and stores various digital data such as static image data, dynamic image data, audio data and music data. This IC memory device functions as an external storage medium of a host device such as a personal digital assistant, a desktop model computer, a notebook model computer, a portable telephone, an audio device or a home electrical appliance.
The operation of such an IC memory device is controlled by the host device via a predetermined interface. Typically, a processing command is transferred from the host device to the IC memory device, thus controlling the operation.
The access speed of the flash memory used in the IC memory device is low. Therefore, in order to reduce a data transfer sequence between the host device and the IC memory device, it is effective to prescribe an interrupt request that notifies of the end of processing from the IC memory device side.